Telephone-exchange system



S. B. WILLIAMS, JR,, AND R. L. QUASS.

TELEPHONE EXCHANGE SYSTEM.

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S. B. WILLIAMS, JR., AND R. L. Q UASS.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED N0v.1s.19|s.'

1,330,417. Patented Feb. 10,1920.

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'8. B. wILLIAIvIs, 1A., AND R L. QUASS.

TELEPHONE EXCHANGE SYSTEM.

APPLlCATlON FILED NOV. Is. 1916. I 1,330,417. Patented Feb. 10,1920.

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S. B. WILLIAMS, 1a., AND R. L. QUASS.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 13, 1916.

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i l l AffS s. B. WILLIAMS, m, AND R. L. QUASS.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. I3, I9I6.

Patented Feb. 10,1920.

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S. B. WILLIAMS, 1a., AND R. L. QUASS.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION man NOV. 13. I916.

Patented Feb. 10, 1920.

s. B. WILLIAMS, JR., AND R. L. uAs s.

. TELEPHONE EXCHANGE SYSTEM.

. APPLICATION FILED NOV 13. 1916- 1,330,417. Patented Feb. 10,1920.

'7 SHEETSSHEET 7.

UNITED STATES PATENT OFFICE.

SAMUEL B. WILLIAMS, J'R., 0F BROOKLYN, NEW YORK, AND RALPH L. QUASS, OE HAWTHORNE, NEW JERSEY, ASSIGNORS TO WESTERN ELECTRIC COMPANY,

INCORPORATED, OF NEW YORK, N. Y.,

ACORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM;

To all whom it may concern:

Be it known that we, SAMUEL B. WIL- LIAMs, Jr., and RALPH L. QUAss, citizens of the United States, residing at Brooklyn, in the county of Kings and State of New York, and at Hawthorne, in the county ofPassaic and State of New Jersey, respectively, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to a system of the call distributing type. Its principal object is to provide a call distributing system having a high degree of flexibility, efficiency and reliability of operatlon.

In systems of the type to which the present invention relates, it is customary to provide automatic switches for extending the circuits of calling lines to operators positions where connection with the lines that are called may be completed. In order to afford the highest degree of flexibility and to enable the apparatus to operate at,its

highest efficiency, it is desirable that each of the subscribers lines shall have access to all of the operators positions 1 and that each operators position shall be accessible from all of the subscribers lines. But Where the exchan e, is a large one serving a great many subscrifiers lines and employing a great many operators positions, such a result may be difficult to attain on account of the physical limitations of the switches that select and connect with the operators positions. Furthermore, the throwing. together into one electrically inter-related group of all the operators positions and all the paths over which the lines have access to them, while desirable from the standpoint of flexibility and efficiency, is objectionable on account of the increased possibility of all service being temporarily shut off on account of some accident occurring in the single group that is thus constituted.

In the present invention, the operators positions and the paths over which they arereached are divided into a plurality of groups. Certain groups of telephone lines normally have access to one group of operators positions, and other groups of lines Specification of Letters Patent. Patented Feb. 10, 1920. Application filed November 13, 1916. Serial No. 131,089.

normally have access to another group of operators positions. But each group of lines is provided with switching ap liances which operate, when for any reason t e operators positions to which the group normally has access cannot be reached or cannot give service, to direct the calls to an- 4 other group of operators positions. Thus the system of the invention realizes the advantages of flexibility and efficiency that arise from giving each line access to a large number of operators positions, while retaining those advantages connected with the use of smaller groups, involving the use of simpler switches for reaching the operators positions and a lessened possibility of the accidental shutting off of service. y

The mannerin which these results are attained may best be explained by reference ing lines that extend to the margins of the drawings, show diagrammatically a preferred circuit organization of such a system.

Referring first to F 1, this illustrates diagrammatically a number of line finder frames FF1, FF-.-2 and FF-8, interconnected by means of finder circuits F-Qr-rl, F C2, etc.'. with a number of cord selector of the line finder frames FF-1, FF2, FF-3, serving as the terminal of a plurality vof'subscribers lines extending to the frame in the line cables LC1,-LC2 and LC3, respectively, and each of the cord selector frames SF1, SF--2, etc., serving as the terminal of a plurality of connecting cord circuits, the conductors of which are carried in the cables OC lOl, OC102,

etc., and OC201, OO202, etc., which extend respectively to the various operators positions of group 1-and group 2.

The line finder frames FF-1,FF-2, etc.,

and the cord selector frames SF -1, SF-2,

etc., withtheir associated switches, may be of the type which is illustrated in Patent 1,177,044 to James L. McQuarrie, 'issu'ed March 28, 1916, towhich more particular reference will be made hereinafter.

In the specific embodiment of the invention diagrammatically represented in Fig. 1, each of the line finder frames FF-1,' FF-2, etc., may'serve as the terminal of five hundred subscribers lines divided into ten groups of fifty lines each. On each side or face of the line finder frame and cooperating with the five hundred lineterminals, which appear on each side or face, there may be thirty elevators or movable switches, each serving as a terminal of an associated finder circuit F'C. Each of the cord selector frames SF-1 SF-2, etc., may serve as the terminal of nineteen groups of connecting cord circuits, each group containing the conductors of twenty-five connecting circuits and extending through the cables 0G to a dlfierent operators position. On each side or face of each cord selector frame SF there may be thirty elevators or switches, each serving as a terminal of one of the finder circuits FC the other terminal of which is a corresponding elevator on an adjacent line finder frame FF. Thus the five hundred telephone lines which terminate on each line finder frame FF have access by way of thirty finder circuits and the cord selector frame on the right to which they extend to the nineteen operators positions, in one group, and by way of thirty fin der circuits and the cord selector frame on the left to which they extend to the nineteen operators positions of another group.

Each line cable LC1, LC2, LC-3, etc., carrying the conductors of five hundred lines, terminates upona different one of the line finder frames FF1, FF2, etc., and also extends to multiple s'pringjacks accessible to all of the positions of group 1 and group 2. It will be understood, of course, that only enough of the whole equipment is shown to illustrate the scheme of interconnection.

In outline, referring to Fig. 1, the operation is. as follows: lVhen a subscriber calls whose line'terminates, for instance, in linefinder' frame FF1, the act of taking the telephone receiver from its hook operates the trip magnet TM on finder frame FF-1 corresponding with the group of fifty lines in which the calling subscribers line is located. It also actuates the starting apparatus SA associated with this line finder frame, and the starting apparatus in operating appropriates one of the finder circuits F'C which has been preselected. and starts the line finding elevator or switch of-that finder circuit hunting for the calling .line.

c ;,If the throw-over apparatus TO associated with the starting apparatus of the finder frame FF1 is thrown toward the right, as shown. in .the drawing, the elevator of one of the finder circuits FC2 serving the right-hand side of the line finder frame FF1 is started. If the throw-over apparatus T0 is -thrownto the left, an elevator associated with one of the finder circuits frame Fl -'1 is. started. This is indicated diagrammatically by the connection of the right-hand contact of the throw-over appa ratus T0 with the finder sequence switches FSS of the right-hand group of finder circuits FC-2, and of the left-hand contact of the throw-over apparatus T0 with the finder sequence switches FSS of the lefthand group of finder circuits F(l1.

FC1 serving the left side of the finder l Assuming that the throw-over switch associated with finder frame FF 1 is in the position shown, one of the finder circuits FC2 is appropriated and its line finder elevator started and brought into engagement with the terminals of the calling line. When this happens, the finder sequence switch FSS of the, finder circuit cooperates with the operators selecting apparatus OSA of the cord selector frame SF2 to select an unengaged operators position'of group 1, start the cord selector elevator of the appropriated finder circuit, trip the set of brushes. corresponding with the selected operators position, and cause the brushes to findthe terminals of an idle cord circuit of that position and make connection with them. Assuming that the position selected is position 2 of group '1, the operator at that position, having communicated with the calling subscriber and learned the number of the line wanted, completes connection with it by inserting the plug of the chosen connecting cord circuit at. her

position into the springjack of the called subscribers line.

The normal position of the throw-over apparatus TO associated with line finder frame FF1 is, as shown, such as to cause the calling lines terminating at that frame to be connected with by the line finder elevators of the finder circuits of group FC-2; and

therefore all of the calls originated by the of cord selector frame SF-2 is such that the operators positions reached through that frame cannot be selected, then the throwover apparatus T0 of line finder frame FC2'to the sequence switches of the finder circuits F(} 1. When. this happens, all calls originated by the lines terminating in finder frame FF1 are extended, in the same manner as has already been indicated, by way of the finder circuits FC1 and the cord selector frame SF 1 to the cord circuits at the various operators positions of g pg )7 In the case of the five hundred lines of line finder frame FF-1," group 1 of 0p-v erators positions is the preferred group, as that is the group to which the calls are normally routed,.and group 2 of operators positions is the alternate group. In the case of the five hundred lines terminating in line finder frame FF-2, the calls are normally directed over one of the finder circuits FG4.- and cord selector frame SF-3 to group 2 of operators positions, and

ferred group and group is the alternate group; and in like manner, the entire series of line finder frames may be so controlled by the associated throw-over apparatus as to make group 1 the preferred group and group 2 the alternate group in the case of part of them, while the reverse may be the case with respect to the rest of them. Or, as will be described hereinafter, the throwover apparatus may be so set or manipulated that the calls of all of the lines of the ex.

change may be directed into either group of operators positions to the exclusion of the other group.

Referring now to the specific embodiment of the invention as illustrated in Figs. 2 to 7 inclusive of the drawing, this embodiment is represented as comprising telephone lines extending from stations as A and A to stationary terminals upon the opposite faces or sides of a line finder frame, the right-hand side of the frame being served by a plurality of line finder switches or elevators G and the left-hand side of the frame being served by a plurality of line finder switches or elevators G. Each line has associated with it a line relay 12 and a cutoff relay 11, and

each grou of fifty lines on the frame has associated with it certain group apparatus designated as LG and LG. The group apparatus is connected through the medium of conductors 57 and 58 with the starting and throw-over apparatus,-which a paratus is common to al of the groups an to the five hundred lines terminating upon the line finder frame, and is shown in Fig. L This common starting and throw-over apparatus is connected through the medium of the conductors 25, 26, 27, 28, 29, 78, 79 and '80 with the apparatus of the group of finder circuits F, F and F associated with the line finder switches or elevators G on one side of the frame, and throu h the medium of the conductors 25, 26, 2 28', 29, 78', 7 9' and 80' with the apparatus of similar finder circuits associated with the line finder elevators or switches G on the left-hand side of the frame. side of the line finder frame may be understood to be precisely the same as those serving the right-hand side of the frame, they are not shown. The finder circuits F, F, F, etc., terminate in cord selector switches or elevators CS, CS, etc., and through the medium of these, operating under the control of the operators selecting apparatus'SF-4, the finder circuits are adapted to have their connections extended to any one of the connecting cord circuits 85, 86, 87 and 88 at any 'one of the operators positions such as are indicated at O and 0. Each one of the connecting cord circuits of the group at each of the operators positions may be equipped as illustrated, and may terminate in a plug 170 which may be inserted in a multiple springjack 14 of a line extending to a called subscribers station A The multiple connection of the circuits of the various operators positions with different cord selector frames, which is shown clearly in Fig. l of the drawing, is indicated in the circuit diagram by the stub connections shown at SF2. These stub connections may be understood to represent connections of the same sort as are shown fully at SF1- in the circuit diagram.

As heretofore stated, the linefinder switches of groups G and G and the cord selector switches CS and CS" may be su-bstantially like the switch illustrated and'described in Patent 1,177,044 to James L. Mc-

Quarrie, issued March 28, 1916. The line finder and cord selector switches are alike in all substantial respects. Each comprises a longitudinally movable shaft 1 carrying as many sets of brushes 2 as there are groups of stationary terminals to be engaged. To move the shaft up, an extension at the lower end of the shaft is brought into engagement with the constantly rotating power mem- As the circuits serving the left-hand ber 3 by means of an idler wheel operated by the up-drive magnet .32 and to move the shaft down, the extension is brought into engagement with the power member 4 by means of an idler wheel operated by the down-drive magnet 62. Normally the brushes of each of the sets 2 are held apart so as toclear the associated terminals by means of a separating cam 5 located'between the innermostbrushes of the set. The cam is rotatablymounted, and when rotated in one direction releases the brushes and permits them to engage theassociated terminals. The tripping or releasing of the so that whichever of the finder switches is caused to move'up has that set of brushes tripped thatcorrespomls with the particular trip magnet 16, 17, that is at the time energized. been in use is returned to its normal position, any of the associated controlling cams 5 that has been tripped is engaged and rotated in a reverse direction to separate its switch springs again and thus render them inactive. Each of the line finder and cord selector switches has associated with it a commutator S which comprises a number of stationary commutator segments and a set of movable brushes carried at the top of the switch shaft 1 and cooperating with the stationary segments. This commutator serves to make and break a number of the controlling circuits in the various stages of the upward movement of the switch shaft.

For controlling the circuits of the organization, there are employed a number of sequence switches which are shown at different points and are designated 100, 200 and 300, respectively. These sequence switches may be of the type disclosed in Patent 1,127,808. issued February 9, 1915, to Reynolds and 'Baldwin. Each consists of an'electromagnetically controlled motor or driving mechanism and a number of associated switch cams. The switch cams associated with each of the sequence switches 100 are designated 101' to 103, inclusive; those associated with each of the sequence switches 200 are designated 201 to 222, inclusive; those associated with each of the sequence switches 300 are designated 301 to 305, inclusive. To each of the contacts associated with the various sequence switch cams are applied certain numerals. These numerals in the case of the cams 101, 201 and 301 indicate the only positions of the associated sequence switch in which these particular contacts are open; the numerals applied to all of the other contacts of'each sequence switch indicate the only positions of the particular sequence switch in which the associated contacts are closed.

\Vheu the finder switch that has The sequence switches 100 merely act as timing switches and have only one resting position. The resting positions of the other sequence switches, and the stages of operation with which these positions are associated, are as follows:

Sequence switch 200.

1. Normal;

. 2. Awaiting starting circuit.

3. Awaiting starting circuit release. 4. Hunting calling line.

6. Awaiting preceding finder circuit. 7. Awaiting operators selecting circuit. '8. Releasing operators selecting circuit.

9. Hunting cord circuit.

Talking. Line finder at telltale. Line finder return. ord selector return.

Sequence switch 300. 1-. Awaiting a. call. 4. Positlon vacant. 17. Posltlon busy.

The operation of the system as illustrated in the accompanying drawings is as follows: lVhen a subscriber calls, the taking of the telephone receiver from its hook closes a circuit in the usual way that causes the energization of the associated line relay 12 at the central oflice. The line relay in operating closes a circuit that extends from battery through the winding of relay 19 of the group in which the calling line is located, contacts 103 (18%, to 19;) of sequence switch 100 of that group, group conductor 18, and

armature and front contact of line relay 12 to ground. Relay 19 in operating closes a circuit that extends from battery, through the right-hand winding of relay 24,- front contact and armature of relay 19, conductor 57, inner back contact and armature of relay 22, left-hand back contact and armature of relay 23, back con-tact and armature of relay 65 to ground. Relay 24 inoperating closes a locking circuit for itself in its left-hand front contact and armature and in doing so causes the operation of the associated tripping magnet 16, the energizing path for the tripping magnet and forthe left-hand or locking winding of the relay 24 bein -by way ofthe left-hand front contact an mature of relay 24, conductor 58, winding of relay 22, left-hand armature and back contact of relay 23, and back contact and armature of relay ()5 tov ground. Relay 24 in operating also closes a circuit that extends from battery through the motor magnet of the associated sequence switch 100, sequence switch contact 102 (18% to 1 and righthand contact and armature of relay 24 to ground. The closure of this circuit moves sequence switch 100 out of position 1, whereupon the switch continues to rotate, un-

der the control of its governing cam 101, until it completes its cycle and again comes to rest in position 1, the circuit by way of cam 102 (-18% to 15;) opening in the meantime as aresultof the release of the relay 24. lVhile the sequence, switch 100 is rotating it maintains open in sequence switch contact 103 (183- to 14) the connection of the relay 19 with the group conductor 18,

so that during this period the relay 19 is not under the control of the line relays 12. During this interval the calling line isfound and the line relay 12 denergized to remove the ground from conductor 18, as will hereinafter he described.

Included in the circuit by way of conductor 58 closed upon the initiation of a call, as described above, is the winding of the starting relay 22. This relay in operating closes the circuit of the starting conductor 129, and in doing so brings about the movement of a line finder switch in one or the other of the groups of switches G and G that have access to the terminals of the five hundred lines in which the line assumed to be calling is located. These two groups are preferably those on opposite sides of the line finder frame; but if desired the switches on one side of the frame may be divided into groups feeding into corresponding groups of operators positions.

T he particular group in which a line finder switch will be started by the operation of the starting relay 22 is dependent upon the condition of energizationor deenergization of the relay 66, and upon the direction in which the preference-switch P is thrown, as will be described hereinafter. Assuming that the relay 66 is deenergized and that the preference-switch P is thrown to the right,

- the starting conductor 129 is connected with the conductor 29 extending to the sequence switch contacts of the finder circuits that terminate upon the line finder switches of group G.

For reasons that will hereinafter be explained, only one of the sequence switches associatedwith the finder circuits of group (1 is in position 2. Assuming that this is the sequence switch of finder circuit F, a circuit is completed that extends from bat- .tery through the left-hand winding of relay 30, sequence switch contacts 206 (2), conductor 29, right-hand contacts P of preference-switch P, right-hand back contact and armature of relay 66, conductor 129, inner front contact and armature of relay 22, lefthand armature and. back contact of relay 23, and back contact and armature of relay 65 to ground. Relay 30in operatin closes a locking circuit for itself that exten s from battery through resistance coil 56, sequence switch contacts 217 (2 to 9), right-handwinding of relay 30, sequence switch contacts 21 6 (2 to 4) and (2 to 9), 1efthand In position 3 of the switch, a circuit is closed that extends from battery by way of the up-drive magnet 32 of the corresponding I li-ne finder switch LF, sequence switch contact 207 (3 to 4), front contact and right hand armature of relay 30, and sequence switch contacts 208 (18 to 14) and (2 to 7) to ground. Theenergization of the up-drive magnet 32 starts the upward movement of the corresponding elevator rod with its as sociated sets of brushes. At the outset of the upward movement of the elevator rod, all of the brush trip levers are moved past the corresponding trip yokes. The only trip magnet that is energized in this case is the magnet 16 which corresponds with the group in which the calling line is assumed to be located; and consequently the only trip yoke in position to engage a trip lever on the elevator rod is the one which controls the brushes 40, 41, 42 and 43 that are adapted to engage the terminals of that particular group of lines. This set of brushes, therefore, is released and made operative, and the other sets are held clear of their associated line terminals. a

As soon as the set of brushes corresponding with the calling line is tripped, the group apparatus, by means of which lines control the brush tripping and line finder starting operations, may be returned to its normal condition. The first step in this restoring operation is effected by the closure of a circuit which is completed by way of the K segment of the line finder commutator immediately after the brushes are tripped. This circuit extends from battery.

' Relay 23, in its right-hand front contact,

closes a, locki'ng circuit for itself and the associated relay 33 that extends by way of conductor 125, left-hand armature and back contact of relay 66, switch-spring P and right-hand contact of the preference switch P, conductor 25, and the sequence switch contacts 210 (25,; to 1) of allof the finder circuits in series, to ground at a point beyond the last switch of the series.

As has already been stated, normally there is only one of the finder circuits with its sequence switch in position 2 awaiting the receipt of a call. When the call comes in this sequence switch is immediately moved to position 3, in the manner described above.

Therefore at this state of the operation the sequence switches of all of the finder cir cuits, being either in position 1 or 1n position 3 and beyond, are in position to close their contacts 210. ,The locking circuit for the relays 23 and 33 is therefore held closed until another one of the finder circuits has its sequence switch moved into position 2 to break the locking circuit in the correspondin some position between 4 and 17, that finder circuit being assumed to be in use, the operation of the relay 33 completes a circuit from battery, through the motor magnet and contacts 203 (1) of the sequence switch of finder circuit F, contacts 211 (1) of the same sequence switch, contacts 211 (3m 17) and (4 to 17) of the sequence switch 200 of finder circuit F contacts 211 (3 to 17) and (3 to 31-) of the sequence switch 200 of finder circuit F that has just been appropriated, conductor 28, right-hand contact and switch spring 19 of preference switch P, conductor 128, and left-hand front contact and. armature of relay 33 to ground. This causes the sequence switch of finder circuit F to move into position 2. At the same time the sequence switch of finder circuit F is moved out of position 3 by the closure of a circuit that extends from battery through the motor magnet and contacts 203 (3) of the sequence switch of that circuit, conductor 27, right-hand contact and switch spring 77 of preference switch P, and right-hand frontcontact-and armature of relay 33 to ground.

As soon as the sequence switch of finder circuit F" moves into position 2, it opens in its contacts 210 the circuit by way of, conductors 25 and 125 which up to this.

moment has maintained relays 23 and 33 energized, and these .relays thereupon rethe calling line is located. As the tripped brushes rise, they come into. engagement successively with the sets of terminals corresponding with the different lines of the group. At the instant of engagement of the brush 42 with the corresponding line terminal 46'of'each line, a circuit is closed that extends from battery'by way of the relay 52, sequence switch, contacts 212 (2 to .4), conductor 50, brush 42, line terminal 46, conductor 53, and winding of cutoff relay 11 to ground. In case a line over which the brushes are passing is busy either as a calling or as a called line, a branch path from battery is closed to conductor 53 which serves to shunt the relay 52 and prevent its operation as the finder brushes pass over the terminals of the corresponding line. that are not busy, the relay 52 is operated as the brushes engage the terminals of such lines. In attracting its armatures, the relay 52 closes a circuit that extends from battery through the lower winding-of relay 37, front contact and lower armature of relay 52, sequence switch contacts 213 (2 to 4), conductor 49, brush 41, line terminal 45, conductor 39 to one limb of the telephone line, thence by way of the path controlled in contacts of the substation switchhook to the other limb of the line, conductor 38, terminal 44, brush 40, conductor 48, sequence switch contact 214 (2 to 4), upper armature and front contact of the relay 52, upper winding of the relay 37 to ground. The circuit traced above is not completed until the finder switch brushes engage the terminals of the calling line, for the reason that the calling line is the only line that has its telephone'receiver off the hook and at the same time is not connected with either by some other line finder or by a connecting cord calling plug. The completion of this circuit energizes the relay 37 and causes that relay to interrupt in its back contact the circuit by way of the left-hand armature and front contact of the relay 30, sequence switch contacts 216, right-hand winding of relay 30, sequence switch contacts 217, and resistance 56 to battery. which circuit has been holding relay 30 locked up from the moment that the relay was first energized upon the receipt ofthe call.

In the case of the lines Relay 30 in releasing its armatures breaks its own locking circuit traced above, and also breaks the previously traced path includin sequence switch contacts 208 right- .hand Trent contacts of. the relay 30, and sequence switch contacts 207, over which current has been flowing to ener ize the updrive magnet 32 of the line fin er. Therefore, the operation of the relay 37 upon the finding of the calling line acts to efiect'the instant deenergization of the up-drive magnet 32 and thus to sto the brushes upon the terminals of the ca ling line.

When the relay 30 is deenergized, as a result of finding the calling line, it also completes a circuit that extends from battery through the motor magnet and contacts 202 (3 to 4) of the sequence switch 200 right-hand back contact and armature oi the relay 30, sequence switch contacts 208 (18 to 14) and (2 to 7), to ground. The closure of this circuit moves the sequence switch out of position '4.

When the sequence switch reaches position 451-, it closes a path for the flow of current through the cut-off relay 11 of the calling line by way of resistance coil 64, sequence switch contact 212' (4% to 124) conductor 50, brush 42, line terminal 46 and conductor 53. The fiow of current in this path operates the cut-oi? relay 11 to disconnect the line relay 12 from the circuit, and that relay in releasing its armature disconnects round from the common conductor 18.

he disconnection of ground from conductor 18 occurs before the timing sequence switch 100 has completed its cycle of rotation and reconnected conductor 18 with relay 19.

The brushes of the line finder switch are now at rest in engagement with terminals of the calling line, the group starting circuit represented by the conductors 57..and 58 and the associated common relay 22 has been released and is in readiness to respond to'another calling line, and the sequence switch of another finder circuit has been moved into position 2, and thus brought into operative relation with the starting conductor 129. The stages 01" the operation that are next to be described have to do with the selection by the appropriated finder circuit of an idle operators position and the selection of an idle connectin cord on that position.

When the fin er sequence switch 200 reaches position 5, it closes a circuit that extends from battery by way of the winding of relay 55 (Fig. 6), conductor 71, and sequence switch contact '218 (5 to 8) to ground. The operation of the relay 55 applies ground' to the conductors 81 extending to all of the operators positions to the connecting circuit terminals of which the cord selector switch of the finder circuit has access. At each of the positions where the operator is at her station and is in readiness to receive a call the associated relay 91 (see Fig. 7) is inert, and the operators telephone sequence switch 300 is in its 1 .osition. Consequently, at each of such positions a circuit is closed that extends from battery, through the winding of associated relay 92, armature and back contact of relay 91, sequence switch contact 304 (l), conductor 81, arma-' movement and comes to rest in position 6.

Here it awaits the closing of a circuit the completion of which is dependent upon the condition of the other finder circuits of the associated group. This .circuit extends from battery through the left-hand winding of the relay 30, contact 219 (6) of the appropriated finder circuit sequence switch, contacts 219 (9 to 4) of the sequence switches of the associated finder circuits preceding it in the series, conductor 76, outer armature and back contact of relay 54, and righthand back contact and armature of relay 61 to ground. This circuit is open either in cam 219 of a preceding finder sequence switch 200 in the series or in contacts of the relays 54 or 61 as long as any other sequence switch of the series is in positions 4 to 9. That is, it is open from the time the line finder switch of an associated finder circuit finds a calling line until the cord finder switch of that circuit has moved far enough to trip the brushes corresponding with the selected group. Not until this has occurred will the above traced circuit of the awaiting finder circuit be closed.

The closure of this circuit causes relay 30 to attract its arma ures and complete a cir-' cuit that extends irom battery through the 'from battery through the winding of relay 54 (see Fig. 6), left-hand back contact and armature of relay 61, conductor 73, and finder sequence switch contact 218 (6% to 8) to ground. Relay 54 attracts its armature and completes a branch of the circuit traced above, which extends from conductor 73 by way of the armature and back contact of the relay 63, front contact and inner armature of relay 54, armature and front contact of relay 77' (which relay is energized, as

previously'describcd, as. a result of the corrcsponding operators position being in readiness to; receive a call), right-hand back contact and switch spring of relay 93 of'the correspondin roup, winding of associated relay 94, win in of relay 93, left-hand switch spring an resting contact of relay 93, conductor 83, left-hand back contact and sition to battery. 9 Upon the closure of the armature of relay 95 at the O operators poabove traced branch circuit the group relays 93 and 94 are energized in parallel with the relay 54. Relay 93 in operating disconnects its own energizing winding and that of relay 94 from the previously-traced path to battery by way of the left-hand back 8 contact and armature of the relay 95, and

connects them in a path which extends from battery byway of the winding of the relay 95 and conductor .84. This causes the relay 95 also to be energized and to interrupt in its left-hand armature and back contact the path by way of conductor 83 over which the relays 93 and 94 were initially energized.

Relay 94 in operating closes a circuit from battery through the winding of the trip magnet 20 corresponding to the selected operators position and to ground by Way of the right-hand armature and front contact 4 of the relay 94. This relay also closes a circuit that extends from battery through the winding of the relay 63 and the left-hand armature and front contact of the relay 94 to ground. The relay 63 in operating closes a branch that extends. from the conductor 73 (grounded at contact 218 (6% to 8) of the line finder sequence switch) through the armature and front contact of relay 63, conductor 72, sequence switch contact 220 (7), v and left-hand winding of relay 30 "to bat- :tery.- Relay 30 attracts its armatures and closes a circuit that extends from battery through the motor magnet and sequence switch contact 202 (7), front contact and right-hand armature of relay 30, sequence switch contacts 208 (18 to 14) and (2 to 7), and thence to ground. The closure of this circuit moves sequence switch 200out of position 7. Furthermore, relay 30 in operating is locked up over a circuit that extends from battery through resistance 56, sequence switch contacts 217 (2 to 9), right- 5 5 hand winding of relay 30, sequence switch conwitch contact 207' (s to 9 right-hand front contact and armature of relay 30, sequence switch contact 218 (8 to 9) and thence to ground. At the outset of the'upward movement of "the-cord finder brush rod the tripextending to the O operators position.

Immediately after the set of brushes is tripped, the common operators selecting circuit is restored so as to be available for the use of other cord finder switches. This is effected throughthe medium ofa circuit that is completed by the grounding ofthe K segment of the cord finder commutator, this segment being so located as to be engaged by its brush immediately after the tripping levers of the sets of brushes pass the associated tripping yokes. The circuit referred to extends from battery, through the Winding of relay 61, conductor 74, sequence switch contact 221 (7% to 8), conductor 180, cord finder commutator segment K and its corresponding brush to ground. ,Relay 61 in operating opens in its left-hand back contact the previously traced circuit by way ofconductor 73 which, up to this time, has been holding energized the relay 95 at the O operators position and the relays 93 and 94 corresponding to this position on the cord finder frame. The release of the relay 94 deenergizes the corresponding trip magnet 20 and the common relay 63. The deenergization of the relay 93 reestablishes, subject to the release of relay 61, the control of other finder circuits over the brush-tripping mechanism of the associated cord finder frame.

Relay 61 in operating closes a locking circuit for itself by way of conductor 73, sequence switch contact 218 (6% to 8), and

thence to ground. It also completes a cir- -cuit that extends from battery through the switch opens its contacts 218 (6% to 8) and 221 (7% .to 8), thus deenergizing relay 61 and again extending conductor 73 to the re- I lay 54 and the conductors over which the operators selection is efl ected. In closing its right-hand back contact upon release,

relay 61' also restores the continuity of conductor 76 and makes it available for moving out of positlon 6 the sequence switch of 1 some other finder circuit which may be waiting for access to the operators selecting circuit.

When the sequence switch 200 is moved cuits located at that operators position.

When a cord circuit is not in use, its corresponding terminal 118 is connected directly to ground; and when the termlnals of such a connecting circuit are encountered, a path is completed that, extends from battery, through the lower winding. of relay 37, sequence'switch contacts 206 (8 to 9), conductor 99, brush 114, terminal 118, conductor 88 of the cord circuit, contact 161, which is closed when the associated cord is not in use, and right-hand back contact and armature of relay 119 to ground. Current flowing in this circuit causes the relay 37 to attract its armature and break the previously-traced circuit by wayof sequence switch contacts 216 and 217 and the right-hand winding of relay 30 which, up to this time, has been holding relay 30 energized.- When the relay 30 is released it opens, in its right-hand v frontcontact, the previously-traced circuit circuit.

present instance as being a cord circuit,

including the up-drive magnet 34, and thus causes the brushes of the cord finder switch to come to rest on .the terminals of the selected cord circuit. The relay 30 in releasing also closes a circuit that extends from battery through the motor magnet and contact 202 (9) of the sequence switch 200,

back contact and right-hand armature of relay 30, and sequence switch contact 218 (8 to 9) to ground. The closure of this circuit moves the sequence switch 200 out of position 9, whereupon it moves under the control of its contact 201 into position'14, which is the talking position of the finder .The connecting circuit to which the finder circuit is thus extended is illustrated in the terminating in a connecting plug 170 and including in its talking conductors 85 and 86 the windings of a repeating coil 159 with a bridged battery, and the usual signal controlling relays 171 and 187. The connecting "1 circuitalso includes a ringing key 120 by means of which current from the ringing generator 181 maybe applied to the circuit of the called line, and a listening key 130 by means of which the connection of the operators telephone 147 vwith the called line may be controlled.

The extension of the. finder circuit to the connectingcord brings about, in a manner which need not be described, the actuation of a signal on the associated operators position which informs the operator that a call is waiting The operators telephone is connected with the circuitby means of the listening key 130; and when the operator has learned the number of the line with which the callingsubscriber desires connection,. she completes the connection by inserting the calling plug 170 into the springjack 14 of that line. Before the plug is inserted, the usual busy test may be made over the path that is shown extending from the tip of the plug by way ofthe armature and back contact of the relay 175. When the plug is inserted, a circuit is closed that extends from battery through the winding of the relay 119, winding-of the relay 175, the cotiperating sleeve contacts of the calling plug 170 and spring-jack 14, and the winding of the cut-off relay 11 to ground. The completion of this circuit causes all three relays to attract their armatures, the relay 119 opening the path to ground of conductor 88, thus rendering the'cdnnecting cord circuit unselectable, relay 175 disconnecting the tip of the plug 170 from the test condu'ctor and completing the talking circuit of the tip strand, and the cut-off relay 11 disconnecting the line relay 12 of the called subscribers line. Ringing current from the ringing generator ,181 may then be applied I to the called subscribers line by closing the contacts of the ringing key 120.

By means of appropriate mechanism, which is disclosed in the patent to S. B. Williams, Jr., No. 1,304,641, issued May 27, 1919, (Serial No. 180,634, filed July 14, 1917), and which it is unnecessary to describe, as it forms no part of the present invention, the extension of the finder circuit to the connecting circuit brings about the opening of the contacts of the switch 161 and the closing of the contacts of the switch 152. The switch 152 corresponds to the left-hand armature and front contact of relay 152 of the above'mentioned Williams patent, and the switch 161 corresponds to cam 404 of the sequence switch 400 of the Williams patent. Theswitch 161 in opening its contacts renders theassociatedcord circuit u'nselectable immediately and in' advance of the opening of the contacts controlled by the relay 119. The closing of the contacts of switch 152 completes a circuit that extends from battery through the winding of relay 15 5, switch contacts 152, conductor 87, con-tact 117 and cooperating brush 113 of the cord selector, conductor 98, contacts 217 (951- to 14) and (12 to 14) of the finder sequence switch, right-hand winding of relay 30,, sequence switch contact 212 (12% to 14), conductor 50, brush 42 and contact 46 of the line finder, conductor current that flows in this circuit keeps the,

relays 155, 30 and 11 energized during the time that the c connection is established. The relay 155 closes a normal break 1n the ring strand 86 of the talking circuit. The

v controlled by the cord circuit relays-171 and .relay 30, as long as it. is energized, pre-v vents the finder sequence switch 200 from moving out of its talking position 14. The 'cut-ofl relay 11 keeps the branch by way of the line relay 12 disconnected from the calling line. i v

At the termination of the conversation the replacing of the telephone receivers on their switchhooks at the calling and called subscribers stations brings about the display of supervisory signals (not shown) 187 in the usual way, and the operator in response to this indication withdraws the calling plug 17 Ofrom the spring-jack of the called subscribers line.

The withdrawal of the plug is accompanied by the opening of the contacts of switch 152. This opens the circuit traced in the preceding paragraph including the relays 155, 30 and 11, and these relays release their armatures. W'hen relay 30 of the finder circuit releases it closes a circuit that extends from-battery through the motor magnet and contact 202 (8 to 14:) of the finder sequence switch, lefthand back contact and armature of relay 30, and armature and back contact of relay 37 to ground. This moves the finder sequence switch out of the talking position 14. When the finder sequence switch reaches position 15 it is moved through that position by means of a circuit that is completed frombattery, through its motor magnet and contact 202 (15), right-hand back contact and armature of relay 30, sequence switch con-- 'tacts 218 (15) to ground. When the line finder sequence switch reaches position'16 a circuit is completed that extends from battery through the down-drive magnet 62 of the line finderv switch, and sequence switchcontacts 208 (16) to ground. As a result, the brushes of the line finder switch are returned to normal.

When the brushes reach their normal position, a circuit is closed that extends from battery, through the motor magnet and contact 205 (16) of the finder sequence switch, conductor 69, segment Y of the line finder commutator and its corresponding energizes .the down-drive magnet .35 and causes the cord selector brushes to return to their normal position. At the end of the downward movement of the brushes a ciru cuit ,is closed that extends from battery through the motor magnet and contact 205 (17) of the finder sequence switch, conductor 31, Y segment of the cord selector commutator and corresponding brush to ground. The completion of. this circuit moves the finder sequence switch 200 out of position 17, after which it returns to position 1 under the control of its cam 201.

The operation that has been described in.

the foregoing is under the assumption that the preference switch P is thrown to the right, as illustrated in the drawing, and that the apparatus and circuits comprised in the group with which the starting circuit is connected under this assumption are in condition to care for the calls that the subscribers lines initiate. The description will now be directed toward the organization whereby the calls that are initiated are autoductors for the switching of which provision is made in the present organizationcin order to give the associated group of subscribers lines control over the finder circuits extending to one or another of two groups of operators positions.

The apparatus for accomplishing this result comprises a preference switch P which may be manually operated, and an automatic throw-over relay 66 controlled through the medium of groups of relays responsive to variousconditions which may arise in the corresponding groups of circuits with which they are associated, in a manner which will be described. The manual preference switch P determines by the direction in which it is thrown the particular group of operators positions to which the calls of the associated group of subscribers lines are directed normally. If its switch levers are thrown to the right thecalls are normally routed to the operators positions to which the finder circuits associated with the line finders of group G have access Ifthe levers of the preference switch P are thrown to the left, the calls are normally routed to the, group of operators positions to which the finder Circuits associated with the line finders of group G on the other side of the framehave access. As soon as the throwover relay 66 is energized, such calls asare initiated during the continuance of this condition are diverted from the operators position associated with the preferred group and are directed to the operators positions in the non preferred or alternate group.

The energization of the throw-over relay 66 is brought about by the operation of either one of the relays 136 and 138. These two relays are operatively associated respectively with the tWo' groups of circuits over which the callsare adapted to be extended I alternatively to the two groups of operators positions. When the particular one of these relays is operated that is associated with the group which is at the time the preferred group, the throw-over relay 66, sub ect to certain conditions, is energized .to route subsequent calls to the non-preferred or alternate group.

Assuming that the preference switch P is.

thrown to the right, making the group served by the line finders G the preferred group, when'the corresponding relay 138 is operated a circuit is completed that extends from battery through the winding of relay 149, closed contacts 8 of the switch S, upper front contact and armature of relay 138, and right-hand contact and switch spring 77 of the preference switch 'P to ground. If

the starting relay 22 is not in its operated condition at this time, relay 149 in operating closes a circuit that extends in two branches from battery to the switch spring of relay 150, one of these branches including the Winding of the relay 150, and the other 1ncluding the winding of the throw-over relay 66 and closed contacts .9 of the switch S; the

circuit thence extending by way of the resting contact of relay 150, closed contacts 8 of the switch S, right-hand armature and front contact of relay 149, and back contact and armature of the starting relay 22 to ground. The throw-over relay 66, in attracting its armatures disconnects the starting wire 129 and the associated locking wire 125 from conductors 29 and 25, respectively, of'the preferred group and connects them with conductors 29' and 25 of the alternate group by way of switch springs 10 and p and corresponding right-hand contacts of the preference switch Consequently such calls as 'may be. initiated thereafter, and while this condition continues, cause the starting of line finders of the alternate group G, and are therefore extended to the cord circuits of the other group of operators in the same manner as that which has hereinbefore been described in detail.

If it is desired that the calls be normally directed to the operators positions served by the finder circuits of the group G of line finders, then the preference switch P will 26, 27 28 and 29, respectively, and ground is disconnected from the upper armature of relay 138 and connected with the upper armature of relay 136, thus making relay 136 effective to control the throw-over operation in the same way asdescribedfor the relay 138. a

In this case when the throw-ove condition arises the relay 136 in operating causes the operation of the throw-over relay 66, and the relay 66 in attracting its armatures disconnects thestarting wire 129 and locking wire 125 from conductors 29' and, 25 of the left-hand group and connects them with conductors 29' and 25-, respectively, of the right-hand girourp. Consequently, such calls as are initiated during starting relay 22 is energized, the previ-.

ously-described circuit, by means of which the throw-over relay 66 and the relay 150. are energized, is open in the outer back contact and armature of the relay 22. Consequently neither of these relays can be oper-' ated until the starting relay 22 is released by the starting of the line finder switch in the manner previously, described.

The preventing of the relay 66 from throwing back from the alternate to the pre-' ferred group while the starting relay 22 is energized is accomplished through the medium of the relay 151. During the time that the starting relay 22 is energized, it completes a circuit that extends from battery, through the winding of the relay 151 and the outer front contact and armature of the relay 22 to ground. The consequent energization of the relay 151 maintains a ground connection in parallel with the ground connection that is kept on the throwover energizing circuit by way of the front contact and left-hand armature of the relay 149. Consequently, if while the starting relay 22 is actuated the relay 149' is released as a result of the deenergization of the relay 136 or 138, as the case may be, the throw-over relay 66 and the relay 150 are still held energized by the ground applied' by the relay 151. Consequently, the" starting w1r.e 129 and the lockin wire- 125 are not shifted back from the a ternate to. the preferred group until after the starting relay 22 is released.

, The object of the above described, provision is to prevent the possibility of the throwing-over or throwing-back operation starting a line finder in each of the two groups in response to the same call. As previously described, the operation of the starting relay 22 causes the instant locking. up of the relay 30 of the finder circuit (see Fig. 5), and this relay starts the associated sequence switch and line finder and remains locked up until the line finder engages the terminals of a calling line. If the throwover relay 66 should either be operated or released an instant after a finder clrcuit relay 30 of the group with which it was at the time connected was operated, the same ground applied. to starting wire 129 in the inner front contact of the relay 22 would operate to lock up a finder circuit relay 30 and start a finder switch of the other group. By holding the throw-over relay 66 either energized or deenergized, as the case may be, as long as the starting relay 22 is energized, this splitting of the start is prevented. The relay 151 is preferably adjusted to act somewhat more quickly than the finder circuit relay 30, in order that when the starting relay 22 operates the relay 151 may be actuated to insure thethrowover relay 66 against releasing before the relay 30 operates to start a finder switch.

Provision is also made for holding up the calls which may be initiated during the time when neither of the two groups of operators is in condition to attend to them. The unavailability of each group .is indicated by the actuation of the associated relays 136 and r 138. When both of the groups are incapable of attending to calls, both of these relays are energized and a circuit is completed that extends from battery, through the winding of relay 139, lower armature and front contact of relay 136, front contact and lower armature of relay 138 to ground. The relay 139 in operating closes a circuit that extends from battery through the winding of relay and the back contact and outer armature of starting relay 22 to ground. Relay 139 also closes a circuit that extends from battery through the winding of the slow-releasing relay 140 to ground. Relay 140 in operating closes a path frombattery for energizing the relay 65 in parallel with the path closed by relay 139. When the relay 65 operates, it closes in its front contact a path to ground for the continued energization of the relay independent of the path 1 by way of the back contact and armature of relay 22. It also opens the ground connection upon which the starting and trlp their energization.

pingcircuits and relays are dependent for Consequently, as long as both of the relays 136 and 138 are energized, the operation; of the relays 19 of the f various subscribersline groups is ineffective to cause the operation of the corresponding trip magnets and the starting of a line finder switch. 1

When the circuits. of one or another of the groups of operators again-become available for extending connections, the release of the corresponding relay 136 or-138 opens the previously-traced circuit including the relay 65, and that relay in releasing restores the control of the starting relay and the. trip magnets to the calling lines. Assuming that the right-hand group G is the preferred group and that it is this group that first becomes available for handling calls, the de energization of the relay 138 not only brings about the restoration of the starting circuit by the relase of relay 65, but it also causes the throw-over relay 66 to throw back from the alternate to the preferred group by the release of the relay 149. It is desirable that the release of the relay 65 shall be delayed until after the release of the relay 66 in order that the starting conductor 129 may not be closed by a waiting call until after the switching of the starting wire from the alternate group to the preferred group has taken place. This result is accomplished by the provision of relay 140, which, on account of being slow in releasing, keeps battery applied for the energization of the relay 65 for an interval after the release of the relay 138, acting through the medium of relay 149, has caused the release of the throwover relay 66.

It will be noted that the energizing circuit of the call-blocking relay 65 is controlled in normally closed contacts of the starting relay 22. This is for the purpose of preventing the relay 65 from being energized to release the relay 22 'and the trip magnet connected in circuit with it prematurely in case the condition that is adapted to cause the energization of the relay 65' arises during a time when the starting circuit is closed.

The conditions which are effective through the medium of the relays 136 and 138 in bringing about the throw-over and call-blocking actions set forth in the foregoing will now be described. One of the circumstances which renders a group of circuits unavailable for handling the calls that are initiated is that in which all of the finder circuits feeding into that particular group are in use. circuit is completed that extends from bat- When this condition exists, a

tery through the winding of the relay 135 The operation of'relay 135 closes a circuit which extends from battery through the. winding of the relay .133 and the front contact and armature of relay 135 to ground;

and the relay 133 in turn closes a circuit that extends from battery through the winding of relay 138 andthe front contact and armature of relay 133 to ground. This operates the relay 138 and, assuming the associated group to-be the preferred group, brings about the results which have previously been described.

Another one of the circumstances which causes the relay 136 or 138 of the associated group to operate to establish the throw-over condition is that in which all of the opera tors positions of the associated group are either vacant or actually busy. When-this. condition exists, a circuit is completed that extends from battery. through the winding of the relay 134 (see Fig. 4), conductor 79, and serially by way of a closed one of two normally open parallel paths at each operators position of the group, to ground at the end of the series. One of these parallel paths at each operators position (see Fig. 7) includes the front contact and armature of relay 193, and the other includes sequence switch contacts 305 (4). When the opera- ,tors position is vacant, the switch lovers of the switch 122 are resting against their outer contacts, and a circuit is adapted to be completed from battery through the motor magnet and contacts 303 (1 and 17) of the operators telephone sequence switch, outer contact and left-hand switch spring of the switch 122 to ground. This circuit prevents the sequence switch from resting in any other position than position 4, and in position 4 the sequence switch contacts 305 (4) above referred to are closed. Consequently, if all operators positions of the group are vacant, the circuit for energizing the relay 134 is completed through the series of closed sequence switch cams 305, and the relay 134 operatesto close the energizing circuit for the relay 138.

If the operators position is not vacant the sequence switch contacts 305 (4) are open, and the continuity of the conductor 79 is under the control of the contacts of the ,relay 193. If the operator is listening in on any one of the connecting cord circuits of her position, the switch 415 of that cord circuit is closed in any suitable manner, and a circuit is completed that extends from battery through the winding of relay 193, 0011- Associated with each connecting cord circuit are contacts 416which'are closed in any desired manner when the connection over that I v} cord circuit is established. When all of the cord circuits of the operators position are in use, a circuitis-completed that extends from battery, through the winding of the relay 194, conductor 148, and to ground by way of the closed contacts'416 of the series of cord circuits. The completion of this circuitenergizes relay 194 which thereupon closes a circuit that, extends from battery through the winding of relay 193, conductor 137 and front contact and armature of relay 194 to ground, thus energizing relay 193. Consequently, whenever the operators position is vacant, or whenever the position ,is occupied and the operator either has her telephone connected with one of the cord circuitsor all of the cord circuits of the position in use, the normal break in the conductor 79 at this position is closed; and when one or another of these conditions exists at all of the operators positions of the group, the path over conductor 79 is completed and the relay 134 is energized to actuate relay 138 as described.

Another circumstance which brings about the energization of one or another of the relays 136 or 138 is the failure of the common operators selecting circuit of the corresponding group to function properly. It will be remembered that the finder sequence switch 200 is moved out of position 4 when the line finder brushes engage the terminals of the calling line; that the sequence switch waits in position 6, the next resting position, until the circuit of conductor 76 to ground is closed by the completion of the operator-selecting operation of some other finder circuit of the group; that the findersequence switch is moved out of the nextresting position, 7, by the setting of the trip magnet 20 or 21 of the'selected operators position; and that it is moved out ofthe next resting position, 8, by the grounding of the K segment of the cord selector commutator as the elevator in rising completes the tripping of the selected brushes. The advance of the finder sequence switch 200 from position 4 to position 9 is unattended by any considerabledelay if the apparatus is functioning properly. If the advance is delayed to an extent which indicates that the apparatus is not operating properly, it is desirable, as this apparatus is common to all of the finder circuits of the particular group, to divert the calls from this group and route them into the other group.

Normally thesequence switches 200 of all of the finder circuits are in one or another of the positions 9 to 4, and a circuit is completed that extends from battery, through the winding ofthe slow releasing relay 160, conductor 70, sequence switch contacts 219 (9 to 4) of all of the finder sequence switches in series, conductor 76, outer armature and back contact of relay 54, and right-hand 

